Display devices typified by liquid crystal display devices have been rapidly improving in performance such as in brightness, resolution, and color gamut. In proportion to the improvement in performance, display devices intended for outdoor use such as portable information terminals and car navigation systems are becoming widespread.
In an environment such as an outdoor space under strong sunshine, a display device may be viewed by a user wearing sunglasses having polarizing function for glare reduction (such sunglasses will be referred to as “polarization sunglasses” hereinafter).
When a display device incorporating a polarizing plate is viewed through polarization sunglasses, the following problems may arise: the polarized light absorption axis of the display device and the polarized light absorption axis of the polarization sunglasses become orthogonal to each other, and consequently the displayed image become darkened and invisible (this phenomenon will be referred to as “blackout” hereinafter); and gradational color unevenness (also simply referred to as “color unevenness” hereinafter) occur due to retardation induced by an optical film disposed in the display device.
PTL 1 proposes means for solving these problems.